Prior Art
Support elements of the type under consideration are intended to assure the most uniform possible distribution of the contact pressure, originating in a wiper arm joined to the support element, to the window of a motor vehicle. By means of a suitable curvature of the unstressed support element--that is, when the wiper blade has lifted from the window--the ends of the wiper strip, pressed all the way against the window in operation of the wiper blade, are urged toward the window by the then-tensed support element, even if the radii of curvature of spherically curved vehicle windows vary in each wiper blade position. The curvature of the support element and thus of the wiper blade must accordingly be somewhat greater than the greatest curvature measured in the swept field of the window to be wiped. Thus the support element replaces the complicated support bracket construction of the kind used in conventional wiper blades, with two spring rails disposed in the wiper strip.
A known support element of this type (French Patent FR 21 91 510) is made from a plastic material, such as a polypropylene. However, it has been found that the strength and thus the elasticity of such support elements meet the demands made of them for only a short time, because the aging process that ensues makes the material brittle and causes it to creep. Especially the more markedly curved regions of the window can then no longer be cleaned, or can be cleaned only inadequately.